This application pertains to a thin-film magnetic writing head, and in particular, to such a writing head having a diamagnetic back gap spacer.
Magnetic flux flowing in the magnetic circuit of an energized thin-film writing head travels through very thin materials. Due to the nature of thin-film head production, the uniform thickness of all parts of various layers in construction is sometimes difficult to achieve. In such cases, writing heads combined to form a printer may have different operating characteristics.
The description which follows is directed to magnetic writing heads of the types disclosed in my U.S. patent application Ser. No. 170,788 entitled "Magnetic Imaging Method and Apparatus" now U.S. Pat. Nos. 4,414,554 and 381,922 entitled "Differential-Permeability Field-Concentrating Magnetic Read/Write Head" (filed May 26, 1982), respectively. Although reference is made to certain specific heads, it will be understood that the invention may be applied equally well to other types of thin-film magnetic writing heads. Writing heads similar to the one described in my prior applications may be excited sufficiently with a current varying from 100 milliamperes to 300 milliamperes. Portions of an inefficient writing head may have a constriction which saturates magnetically before enough flux flows through the writing gap of the head to form a desired magnetic image in a magnetic-image storage medium.
It is therefore a general object of this invention to provide a magnetic head which overcomes the above-noted disadvantage.
More specifically, it is a desired objective to provide such a writing head which may be driven hard enough to provide sufficient flux in even the least efficient heads without saturating any of the heads.
Thin-film magnetic heads constructed according to my prior applications are characterized by sheet-like layers which are placed relative to each other in order to form a magnetic circuit. Typically, one magnetic layer forms a base on which additional layers are applied. The base layer is magnetically spaced from an overlayer of magnetic material with a surface of each of these two layers forming the writing gap. At a position spaced from this gap, the two magnetic materials are in contact in order to complete the magnetic circuit. Electric current-carrying coils are disposed relative to these two magnetic materials in order to induce the flow of flux in them.
Applicant, by this invention, applies a layer of diamagnetic material in the back gap region in order to increase the reluctance of the magnetic path through this portion. This tends to equalize the reluctance through this new back gap with that of the leak or shunt flux which travels between the two magnetic layers intermediate the front and back gaps. Such construction reduces the amount of flux actually traveling through the back gap as compared to such a head not having the back gap. It can therefore be driven harder in order to achieve the desired flux level without saturating that portion of the head associated with the back-gap flux path.
These and additional objects and advantages of the present invention will be more clearly understood from a consideration of the drawings and the detailed description of the preferred embodiment.